fix: UI redesign — horizontal instance rows, proper scaling, readable tag cards

- Backend: add replicas field to InstanceResponse (extracted from values.replicaCount)
- InstanceCard: complete redesign as horizontal row layout
  - Status bar | Name+Chart | Replicas +/- | Action buttons
  - Scale controls show for deployed AND failed statuses (scale to 0)
  - Fix replicas display using new instance.replicas backend field
- InstancesManagementPage: vertical row list + onScale callback to update state
- TagCard: restore proper padding (p-4), min-width, readable button sizes
- ArtifactBrowserPage: reduce grid density (sm:1 md:2 lg:3)
- ModifyModal: simplify to YAML-only editing with current values pre-populated
  - Remove schema-based form generator
  - Keep values-diff as collapsible reference panel

frontend/src/features/artifact/instances/pages/InstancesManagementPage.tsx

@@ -188,6 +188,22 @@ const InstancesManagementPage: React.FC = () => {
     };
   }, [autoRefresh]);
 
+  const handleScale = useCallback((updatedInstance: InstanceResponse) => {
+    setInstancesByCluster((prev) => {
+      const next = new Map(prev);
+      for (const [clusterId, insts] of next) {
+        const idx = insts.findIndex((i) => i.id === updatedInstance.id);
+        if (idx !== -1) {
+          const updated = [...insts];
+          updated[idx] = updatedInstance;
+          next.set(clusterId, updated);
+          break;
+        }
+      }
+      return next;
+    });
+  }, []);
+
   const handleModify = useCallback((instance: Instance) => {
     setModifyInstance(instance);
   }, []);
@@ -421,7 +437,7 @@ const InstancesManagementPage: React.FC = () => {
                         </p>
                       </div>
                     </div>
-                    <div className="grid grid-cols-1 md:grid-cols-2 xl:grid-cols-3 gap-4">
+                    <div className="flex flex-col gap-2">
                       {instances.map((instance) => (
                         <InstanceCard
                           key={instance.id}
@@ -429,6 +445,7 @@ const InstancesManagementPage: React.FC = () => {
                           onModify={handleModify}
                           onTerminate={handleTerminate}
 
+                          onScale={handleScale}
                           onViewEntries={handleViewEntries}
                           onViewDiagnostics={handleViewDiagnostics}
                         />